1. Field of the Invention
The present invention relates to a magnetic resonance imaging (MRI) apparatus and a radio-frequency (RF) coil that is connected to the MRI apparatus and receives a magnetic resonance signal that a subject generates, and particularly, relates to a decoupling of an RF coil device where a plurality of elements (coil elements) are arranged.
2. Description of the Related Art
A method has been known in which a plurality of elements are arranged at a desired region of a subject that should be imaged, and a magnetic resonance signal is detected from the subject via each of the elements; then, an imaging processing is performed relative to each of the detected magnetic resonance signals to generate image data in a plurality of groupings; thereafter, the respective pixel data corresponding to the same space position (a single complex signal or an one-dimensional complex signal being equal to a spectral signal) are multiplied by a weighting function that has been determined in advance based on a distribution of a radio-frequency magnetic field that each element generates, the resultant products are summed to generate each pixel data, and pixel data in the desired region are integrated; accordingly, an image having high signal-to-noise ratio is obtained.
In such a method, because the magnetic resonance signals are simultaneously observed by use of the elements within a time necessary for obtaining one image, it is required to prevent coils from mutually coupling (hereinafter, “decoupling”) in such a manner that the elements do not constantly interfere with each other; in other words, that even when a radio-frequency current having a predetermined frequency is flowing in one element, the radio-frequency current does not flow in other elements.
In the technology disclosed in the U.S. Pat. No. 4,825,162, two elements, which have been arranged in a line on a predetermined arrangement plane surface, are overlapped only at an area determined by the area encircled by the coil on the arrangement surface, whereby the decoupling is performed as a state where, among magnetic fields generated when the current is flowing in one element, a summation of the magnetic fields, which interlink with another element, becomes zero.
On the other hand, a radio-frequency coil device, which is connected with a magnetic resonance imaging (MRI) apparatus to receive the magnetic resonance signal generated from the subject, generally has heavy weight. Therefore, in a method disclosed in JP-A 2006-14823 (KOKAI), a dividing/joining is performed between two adjacent elements.
However, in a decoupling method described in the U.S. Pat. No. 4,825,162, it is necessary to overlap two elements at a division/join portion of a case in the arrangement plane surface. As a result, the method had an unresolved issue, for example, that a shape of the case at the portion to be overlapped had to be thinly designed, or that the case was not capable of being divided at a surface perpendicular to an alignment direction of the elements due to a necessity for overlapping, whereby the division/join portion became uneven.